Apparatus for inspecting sheet materials and conveying device used therefor

ABSTRACT

The sheet material inspection apparatus has a pitch detection section for detecting pitches between sheet materials on a conveying path and a control section which effects so that the sheet material is inserted from a predetermined position of a groove of a rotary body (impeller) by adjusting rotating speed of the rotary body or by using auxiliary conveying path even if a pitch deviation is produced. The sheet material conveying device for conveying sheet materials has a conveying unit which includes pairs of rollers disposed away a predetermined distance from each other, a belt stretched between the pairs of rollers and wound on the rollers through only a predetermined angle; and a guide member disposed between the pairs of rollers so that its upper surface is located more downward by a predetermined spacing than a conveying surface of the belt. Sheet materials are supported between the belt and the guide member and conveyed by driving the belt, which enables high-speed, and less damage, in conveying.

BACKGROUND OF THE INVENTION

The present invention relates to an inspection apparatus for detectingwhether collected sheet materials are normal or damaged and true orfalse and for re-accumulating disposable sheet materials and reusablesheet materials and to also a sheet material conveying device suited tothis sheet material inspection apparatus.

To start with, a conventional sheet material inspection apparatus willbe explained. The sheet material inspection apparatus is an apparatuswhich consecutively takes out collected sheet materials accumulated andfed in at a minute pitch by a take-out unit and thereafter checkswhether the sheet materials are normal or damaged and true or falsewhile conveying them on a belt at a high speed. The sheet materialinspection apparatus then determines whether the individual sheetmaterials are to be disposed of or are reusable, thereafter distributesthe sheet materials to branched conveying paths and re-accumulates thedisposable sheet materials and the reusable sheet materials, separately.

The sheet materials accumulated as the disposable sheet materials bythis apparatus are thereafter shredder-processed. A processing speed ofthe sheet materials in this inspection apparatus is on the order of20-30 sheet materials/see, and a conveying velocity is always keptconstant at 8 m/s.

FIG. 1 illustrates a construction of a sheet material conveying deviceemployed in the conventional sheet material inspection apparatus. Thetransfer of the sheet materials involves independent driving sources andis conducted in such a way that the sheet material is grasped from attwo portions in the crosswise direction by flat belts 61, 62 whoseconveying surfaces are closely fitted to each other. These belts aredriven by motors connected to drive rollers. Driving the belts at a highspeed normally entails using motors each having a capacity on the orderof several hundreds Watt.

As illustrated in FIG. 1, the rollers are disposed alternately on bothsides of the conveying path to ensure the close fit between the belts.In the case of such a construction, the above and below belts have atrace of speed-difference, and, hence, a frictional force needs to beapplied on both of the belts. For this purpose, the resistance of theconveying system is large, and a large force is required for driving thebelts. Further, the belts run with a trace of oscillations in thecrosswise direction, but, because of the surfaces being in contact witheach other, the belts experience influences of the oscillations on eachother. There exists a possibility in which this may cause the belts tocome off the rollers. Moreover, the belts always press the upper andlower surfaces of the sheet material, and, consequently, there arises aproblem in which the sheet material surface is concealed; and locationsfor detection are limited.

FIG. 2 depicts a conveying mechanism adopted in the case of conveyingsheet materials at a low velocity. The sheet material is grasped betweendrive rollers 71 and rollers 72, and an up-and-down guide 73 is disposedbetween the rollers. Down-sizing and a reduction in weight in terms ofthe mechanism are attainable with this system. However, a leading edgeof the sheet material is completely free between the guides andtherefore collides with the rollers, easily resulting in damage. Adefect is that this system is not suitable for conveying the sheetmaterials at a high velocity. Furthermore, the following problem alsoarises. A dispersion in the driving force between the respective rollersis produced by extrinsic factors such as abrasions, contaminations, andthe like, on the roller surfaces. This dispersion in the driving forcein turn causes a slippage, resulting in a difference in the conveyingvelocity of the sheet material between the respective rollers. As aresult, a jam can easily occur.

The take-out unit for feeding out the sheet materials to the conveyingpath is constructed of a holed rotor for performing intermittentrotations and a static chamber connected to a vacuum pump. Every timethe rotor stops, the take-out unit absorbs the sheet materials one byone from a stack of sheet materials accumulated and pulls it off thestack of sheet materials. The take-out unit thereafter puts the sheetmaterial into the conveying system at a predetermined sheet materialpitch (interval between the leading or trailing edges of the sheetmaterials fed adjacent to each other). A slight pitch error produced onthe occasion of this take-out operation, means that the sheet materialshaving a minute pitch error are consecutively fed in the conveyingsystem.

FIG. 3 schematically illustrates a structure of a sheet materialaccumulating unit in the prior art sheet material inspection apparatus.This sheet material accumulating unit is constructed mainly of anaccumulation impeller 74. The accumulation impeller 74 is a rotary bodyhaving spiral blades at equal intervals with spiral grooves therebetweenabout the center thereof. The impeller 74 is belt-driven by a steppingmotor 78. The sheet material fed in is stopped upon an insertion intothe groove, thereafter scraped out of the groove and thusre-accumulated. The sheet materials are then transferred to the nextprocessing.

Herein, for preventing a damage of the sheet material due to a jam and acollision with a blade, there is the need for assuring that only onesheet material is surely inserted into one line of groove. That is, thesheet materials fed in could have, as stated above, a pitch error.Accordingly, the sheet material accumulating unit is required to absorbthis pitch error by use of some means and ensure the insertion of thesheet materials into the accumulation impeller 74. Then, according tothe prior art, one point at a groove entrance of the accumulationimpeller 74 is defined as an insertion point 75, and the control iseffected to make the leading edge of the sheet material reach thisinsertion point 75.

Given next is an explanation of a control method of the accumulatingunit in the conventional sheet material inspection apparatus.

A photoelectric sensor 76 is placed in a position across on theconveying path spaced away approximately 1 pitch from the accumulationimpeller 74. When sheet material traverses this portion, an output ofthe sensor changes, thus detecting the leading edge of the sheetmaterial. A rotary encoder 77 is connected to a motor 78 for driving theaccumulation impeller 74, whereby a position of the in-rotation bladecan be detected.

The sheet material leading edge reaches an optical path of thephotoelectric sensor 76 and intercepts a beam of light, and, thus, thesensor output changes. Then, with this output serving as a trigger, acontrol unit (not shown) reads a value of the encoder 77 and predicts aninsertion position of the relevant sheet material into the groove whenthe accumulation impeller 74 rotates at a standard rotating speed. Atthis time, if the sheet material deviates from the insertion point 75 ofthe groove, the control is carried out to correct this deviation. Thatis, if the leading edge of the sheet material is ahead of the insertionpoint 75 at the groove entrance, the control unit controls the steppingmotor 78 to increase the rotating speed of the accumulation impeller 74.In the reverse case, the control unit controls the stepping motor 78 todecrease the rotating speed of the accumulation impeller 74. In anycase, the rotating speed of the accumulation impeller 74 is determinedto make the sheet material leading edge coincident with the insertionpoint. Thus an arithmetic operation is performed each time the sheetmaterial reaches the position of the photoelectric sensor 76. Therotating speed of the accumulation impeller 74 is varied at all times tocorrect the pitch error between the respective sheet materials. For thisreason, the stepping motor 78 always needs a control torque for anacceleration and a deceleration.

The sheet materials taken out are consecutively fed to the accumulationimpeller 74. If the sheet material pitch does not undergo an influenceby a disturbance or the like during the feed, however, it follows thatthe sheet material pitch just after being taken out continue to be kept.On the other hand, since a positional relationship between the bladesadjacent to each other is fixed, the grooves of the accumulationimpeller 74 can not be properly varied corresponding to the sheetmaterial pitch. Accordingly, if the insertion position is shifted with achange in the rotating speed of the accumulation impeller 74 for an i-thsheet material, this shift directly turns out to be a deviation quantityof the (i+1)-th sheet material with respect to the accumulation impeller74. That is, depending on the way how the sheet material pitch isscattered, if only the insertion position of the just-before sheetmaterial is considered, the deviation quantity with respect to the sheetmaterial subsequent thereto becomes excessive, As a result, a controlquantity of the accumulation impeller 74, i.e., a control torque of themotor, becomes excessive, and hence there is a possibility of beingincapable of control due to the fact that the motor is out of step.Particularly when speeding up the apparatus, this problem turns out alarge obstacle.

In the prior art sheet material inspection apparatus, the insertionposition is determined by only the sensor disposed immediately in frontof the accumulating unit. Therefore, if the processing speed of thesheet materials is increased, it follows that the control torque neededfor the stepping motor for rotating the accumulation impeller increases.This probably results in the incapability of control due to the steppingmotor being out of step. Accordingly, the processing speed isconditioned by the control torque of the stepping motor, which hindersthe speed-up thereof. For this reason, a high-speed and high-torquemotor is needed. However, an unreasonable increment in the motorcapacity brings about increases in size, in weight and in cost of theapparatus.

Furthermore, in the sheet material inspection apparatus using theconventional belts, it may happen that the belts come off A preventionof this requires a long time for strict adjustments of a belt tension, aroller inclination, and the like, and the productivity is not thereforefavorable. Also, when conveying the sheet materials at high velocity,the motor increases in size, and the structure for attaining thedown-sizing and the reduction in weight is hard to realize. The rollerconveying system also easily damages the sheet materials and thereforeunsuitable for high-speed driving.

SUMMARY OF THE INVENTION

Under such circumstances, it is a primary object of the presentinvention to provide a sheet material inspection apparatus capable of ahigh-speed accumulation without increasing a control torque of a motorfor driving an accumulation impeller.

It is another object of the present invention to provide a sheetmaterial conveying device in which the sheet material is hard to damage,and that has a simple structure.

According to the present invention, there is provided an apparatus forinspecting sheet materials, comprising:

conveying means for sequentially conveying a plurality of sheetmaterials;

a rotary body, having a plurality of grooves formed in the peripherythereof enough to permit insertions of the sheet materials, forreceiving the sheet materials one by one in the respective grooves whilerotating the sheet materials fed from said conveying means;

accumulating means for accumulating the sheet materials inserted intothe grooves of said rotary body;

detecting means for detecting a pitch between the sheet materials fed onthe conveying unit; and

control means for performing control so that the sheet material isinserted from a predetermined position of the groove of said rotary bodyon the basis of the pitch between the sheet materials that is detectedby said detecting means.

In the sheet material inspection apparatus according to this invention,a pitch between the sheet materials to be fed is detected by a pluralityof detecting elements provided on a conveying path. Based on thisdetected pitch between the plurality of sheet materials, a control uniteffects the control so that the sheet material is inserted from apredetermined position of a groove of a rotary body (impeller). Even ifa pitch deviation is produced when taking out or conveying thesubsequent sheet materials, the proper sheet material insertion into therotary body can be performed by making use of all the data about thesheet material pitches between the individual sheet materials existingon the conveying path ranging from a take-out unit to an accumulatingunit.

According to an embodiment of adopting a control of rotating speed ofthe impeller, while referring to the sheet material pitch data, if asheet material pitch between a certain sheet material and a sheetmaterial just before it is larger or smaller by a fixed quantity than astandard pitch, a driving system of the rotating impeller is acceleratedor decelerated during a passage of the relevant sheet material on theconveying path of the auxiliary feeding unit. Accordingly, the sheetmaterial is inserted in a predetermined insertion range of theaccumulation impeller, thus effecting the control. It is thereforepossible to reduce an increment quantity of the control torque of theaccumulation impeller.

Further, according to an embodiment of adopting an auxiliary conveyingmeans of the sheet material inspection apparatus of this invention,while referring to the sheet material pitch data, if a sheet materialpitch between a certain sheet material and a sheet material just beforeit is larger or smaller by a fixed quantity than a standard pitch, adriving system of the auxiliary conveying means is accelerated ordecelerated during a passage of the relevant sheet material on theconveying path of the auxiliary conveying unit. The sheet material pitchbetween the relevant sheet material and the sheet material just beforeit is thereby corrected, thus restraining a scatter in terms of thesheet material pitch down to or under a predetermined quantity. Thesheet material is inserted in a predetermined insertion range of theaccumulation impeller, thus effecting the control. It is thereforepossible to further reduce an increment quantity of the control torqueof the accumulation impeller.

Moreover, according to the present invention, there is also provided asheet material conveying device for conveying sheet materials, having aplurality of conveying unit comprising:

a pair of rollers disposed away a predetermined distance from eachother;

a driving belt stretched between said pair of rollers and wound on saidrollers through a predetermine angle; and

a guide member disposed between said pair of rollers so that its uppersurface is located more downward by a predetermined spacing than aconveying surface of the driving belt, said conveying surface areopposed to said rollers, whereby the sheet materials are supportedbetween said driving belt and said guide member and being conveyed withthe driving of the belt.

The sheet material conveying device of the present invention has guidesdisposed in face-to-face relationship with belts wound on feedingrollers but provided at a fixed interval on a belt conveying surfacebetween rollers. The feeding rollers are disposed to set the centers ofcurvatures in the same direction, and, hence, increases a contact forcebetween the sheet material and the belt due to a generation of acentripetal reaction force on the belt by a high-speed feed. The sheetmaterial can be therefore fed by an extremely small amount of drivingforce. Further, the number of belts can be decreased in terms of itsstructure as compared with the example of the prior art, and down-sizingof the mechanism is attainable. In addition, the belts are driven with asmall resistance and can be readily driven at a high speed. Further, thebelts do not come off, and this eliminates the necessity for adjusting abelt tension, and roller inclination, and the like. The time formanufacturing and adjusting the apparatus can be reduced very much.Also, one side of the sheet material is always pressed against theconveying belt, and consequently there is no possibility of damaging thesheet material due to a flip of the sheet material between the rollers.Further, a conveying posture correcting (skew) mechanism for the in-fedsheet material can be easily incorporated by taking the presentstructure, and a more stable feed detection system can be constructed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will becomeapparent during the following discussion in conjunction with theaccompanying drawings, in which:

FIG. 1 is a constructive view of a sheet material conveying deviceemployed in a conventional sheet material inspection apparatus;

FIG. 2 is a view illustrating a conventional conveying mechanism adoptedin the case of conveying the sheet materials at a low velocity;

FIG. 3 is a schematic constructive view of a sheet material accumulatingunit of the conventional sheet material inspection apparatus;

FIG. 4 is a schematic constructive view illustrating the wholeconstruction of a sheet material inspection apparatus according to anembodiment of the present invention;

FIG. 5 is a block diagram showing a configuration of a control system ofthe sheet material inspection apparatus of an embodiment of the presentinvention;

FIG. 6 is a schematic constructive view of a sheet material take-outunit of the sheet material inspection apparatus of an embodiment of thepresent invention;

FIGS. 7A-7D are views of assistance in explaining procedures of takingout the sheet materials in the sheet material inspection apparatus of anembodiment of the present invention;

FIGS. 8A-8C are schematic constructive views each showing a sheetmaterial conveying unit of the sheet material inspection apparatus of anembodiment of the present invention;

FIG. 9 is a timing chart showing how a sheet material pitch is detected;

FIG. 10 is a schematic constructive view of a sheet materialaccumulating unit of the sheet material inspection apparatus of anembodiment of the present invention;

FIG. 11 is a view of assistance in explaining an insertion width in anaccumulation impeller of the sheet material inspection apparatus of anembodiment of the present invention;

FIG. 12 is a flowchart showing a state of control of an accumulatingunit of the sheet material inspection apparatus of an embodiment of thepresent invention;

FIG. 13 is a graphic chart showing an effect based on a control systemof the sheet material inspection apparatus of another embodiment of thepresent invention;

FIG. 14 is a schematic constructive view of an auxiliary conveying unitof the sheet material inspection apparatus of an embodiment of thepresent invention;

FIG. 15 is a view fully illustrating a configuration of a conveying pathshown in FIG. 4;

FIG. 16 is a view showing a configuration of a belt-to-beltreceiving/conveying unit of the sheet material inspection apparatus ofthis invention;

FIGS. 17A-17C are constructive views showing another example of theconveying unit;

FIG. 18 is a constructive view showing an example of modification of thereceiving/conveying unit shown in FIG. 16;

FIG. 19 is a constructive view showing an example where a plurality ofdetecting units are arranged on a conveying path; and

FIGS. 20A-20C are constructive views illustrating a construction of aconveying device in yet another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinafter be fully discussed by way ofembodiments with reference to the accompanying drawings.

FIG. 4 is a constructive view illustrating the whole construction of asheet material inspection apparatus according to an embodiment of thepresent invention. The sheet material inspection apparatus isconstructed of a take-out unit 1, a conveying (detecting) unit 2, aseparating unit 3 and an accumulating unit 4 that are disposed insequence. Sheet materials 10 are fed in a stacked state into thisapparatus by a conveying mechanism which is not shown. The sheetmaterials 10 are separated one by one by a take-out rotor 11 and putinto a conveying path constituting a conveying unit 2. A detecting unit(not shown) is disposed above the surface of the sheet material 10 onthe conveying path 20. The detecting unit checks each of the sheetmaterials 10 as to whether the sheet material 10 is normal or damagedand true or false. The accumulating unit 4 is separated into a reusablesheet material accumulating section 4a and a disposable sheet materialaccumulating section 4b. As a result of inspecting, the sheet materials10 are distributed in their conveying directions. This distribution isdone through a distribution gate 31 provided on the conveying path 20.An accumulation impeller 41 is provided on each of the accumulatingsections 4a, 4b, thereby receiving but stopping and re-accumulating thesheet materials 10 fed at a high velocity. The reusable sheet materialsare stacked in a post-processing unit (not shown) and fed out of thepresent apparatus. On the other hand, the disposable sheet materials aresent to a disposable processing unit (shredder, not shown).Photoelectric sensors for inspecting a passage of the sheet material 10are provided in several positions on the conveying path 20. Thephotoelectric sensors are employed for checking take-out of the sheetmaterial 10, confirming the passage of the sheet material on theconveying path and checking an insertion thereof into the accumulatingunit 4 and calculating a pitch of the sheet materials. Herein, the sheetmaterial pitch implies an interval between the leading or trailing edgesof the sheet materials fed adjacent to each other. Further, thephotoelectric sensor is capable of detecting abnormalities(abnormalities in sheet material length and in sheet material pitch) inthe sheet materials 10 on the conveying path 20. Particularly,photoelectric sensor 51a and 51b disposed just behind the take-up roller11 serve to calculate the sheet material pitch immediately after takingout the sheet materials 10. The photoelectric sensors 51a and 51bcalculate the sheet material pitch, and, if an abnormal pitch is caused,the system quickly detects this abnormality and takes a proper measure.

FIG. 5 is a block diagram illustrating a construction of a controlsystem 100 of the sheet material inspection apparatus according to thisinvention.

This microcomputer-based control system 100 includes an arithmetic unit101 for effecting a variety of arithmetic operations, a memory 102 forstoring an item of sheet material pitch data which will be mentionedlater. The control system also includes a drive control unit 103 fordriving a drive motor 120 for a belt or the like on the basis of anarithmetic result given by the arithmetic unit 101. Output signals of avariety of sensors 110 are given to this control system, and, afterbeing rearranged in a data format by the arithmetic unit 101, thearithmetic and storing operations are performed.

FIG. 6 depicts a construction of the take-out unit. FIG. 6 illustrateshow the sheet materials are taken out. The take-out roller 11 is athin-walled roller including a suction hole 16 (see FIGS. 7A and 7B) cutin the peripheral side surface. The take-out roller 11 is intermittentlydriven by driving a gear, a cam or a servo motor so as to temporarilystop in such a position that the suction hole 16 comes in to aface-to-face relationship with a sheet material surface within onerotation. A sealed static chamber 12 is accommodated in the interior ofthe take-out roller 11 but connected to an external vacuum pump 13. Anair space within the chamber 12 is kept at a negative pressure withrespect to the atmospheric pressure by the vacuum pump 13. If thesuction hole 16 of the take-out roller 11 and a position of a notch 17of the chamber 12 are coincident in the stop position of the take-outroller 11 (FIGS. 7A and 7B), the sheet material 10 on a sheet materialfeed board 14 is separated from a stack of sheet materials thereunderand sucked by the suction hole 16 when the take-out roller 11 is stopped(FIG. 7C). Then, when the take-out roller 11 starts rotating (FIG. 7D),the sucked sheet material 10 is raised along the side surface of therotor, and the leading edge thereof is inserted into the conveying path.Hereat, the sheet material is separated unchanged from the side surfaceof the rotor and then fed. In this case, when the take-out roller 11starts rotating after sucking the sheet material 10, a stack of sheetmaterials thereunder may be slightly pulled due to an influence of africtional force, resulting in a positional deviation. Further, forpreventing two sheet materials from being taken out at one time, theunderside of the sheet material passing is sucked weakly by a two-sheetmaterial take-out preventive block 15. The second sheet material isherein stopped but not inserted into the conveying unit. At the nexttake-out timing, this sheet material is sucked by the take-out rotor 11and then fed.

FIG. 9 is a timing chart showing how the sheet material pitch isdetected. The detection of the sheet material pitch involves the use ofa timer, wherein a signal of the photoelectric sensors 51A and 51B shownin FIG. 4 serves as a trigger. When the leading or trailing edge of thesheet material traverses between the photoelectric sensors 51A and 51B,sensor outputs change from an H-level to an L-level. However, thissignal serves as the trigger, and a timer signal may be taken in. Ani-th sheet material pitch P_(i) is a time difference between a timervalue T_(i) taken at an i-th time by the detecting unit and a timervalue T_(i+1) taken at an (i+1)th time. The sheet material pitches P_(i)are stored sequentially in the memory.

FIG. 10 schematically illustrates a construction of the accumulatingunit. The accumulation impeller 41 is rotationally driven by a steppingmotor 42. A rotary encoder 43 is belt-connected to the motor shaft andworks to monitor a rotational position of the accumulation impeller 41,and an encoder output thereof is supplied to the control unit (notshown).

FIG. 11 shows a construction of the accumulation impeller. Thisaccumulation impeller 41 has twelve lines of spiral grooves formed atequi-angles on a cylinder. An insertion width of the sheet material intothis groove falls within a range of central angles θ1 to θ2, wherein thefiducial point is the tip of the blade of the accumulation impeller 41.A set position of this insertion width is determined in consideration ofthe sheet material length, a sheet material conveying velocity, thenumber of groves and a rotating speed of the impeller. Namely:

    L/V<(360/N-θ2)/W                                     (1)

where L is the sheet material length, V is the sheet material conveyingvelocity, N is the number of groves, and W is the rotating speed of theaccumulation impeller. If this formula is not satisfied, it follows thatthe sheet material collides with the accumulation impeller 41. Then, theangle which should be selected is θ2 satisfying the formula (1). Fromthe above, θ1, θ2 which determine the insertion width are determined inthe following range:

    0<θ1<θ2<(360/N-L·W/V)                 (2)

Further, a position given by (θ1+θ2) /2 is set as an original point, andtherefore:

    θe=(θ2-θ1)/2                             (3)

When this formula (3) is established, ±θe is the insertion width.

Referring back to FIG. 10, a scraping plate 44 is provided on the sidesurface of the accumulation impeller 41. The sheet materials inserted inthe accumulation impeller 41 are neatly arranged by the scraping plate44, and the leading edges thereof fall down along the scraping plate 44with rotations of the blades, thus re-accumulating the sheet materials.

An insertion detecting sensor 45 is disposed on the circumference of theaccumulation impeller 41. This insertion detecting sensor 45 isconstructed of a light emitting element and a light receiving element,and its output changes when the sheet material passes by. The insertionof the sheet material into the accumulation impeller 41 can berecognized by placing the insertion detecting sensor 45 to traverse theconveying path slightly in front of a point at which the sheet materialreaches an entrance of the accumulation impeller 41, i.e., anintersection between the conveying path and a line of outer shape of theaccumulation impeller 41. An insertion position of the sheet material ata groove entrance of the accumulation impeller 41 can be detected byreading a value of the rotary encoder 43, wherein the output of thisinsertion detecting sensor 45 serves as a trigger. Items of data aboutthe insertion position and the rotating speed of the accumulationimpeller are fed back to the control system. Then, a controlcharacteristic can be also improved by changing a weighing coefficientof an evaluation function which will be stated later.

FIG. 12 is a flowchart showing a procedure where the control system 100controls the accumulating unit. The accumulating unit is controlled by asignal of the controller. The rotating speed of the accumulationimpeller is determined by use of data about the sheet material pitchesof the sheet materials from the one just before being inserted to theone located a plurality of sheet materials behind. This aims atdecreasing a peak of control torque of the stepping motor 42 for drivingthe accumulation impeller 41, wherein an item of control data is thearrangement of the sheet materials from the one just before theinsertion to the one located the plurality of sheet materials behind.

Detected as shown in FIG. 12 is that the output of the sensor 51disposed immediately after the take-out roller 11 changes from HIGH toLOW (step S101). The sheet material pitch Pi is calculated from thisfall-to-fall time (step S102). Thus obtained i-th and subsequent sheetmaterial pitches Pi, Pi+1, . . . are stored in the memory.

The sheet materials are fed on the conveying path, and the photoelectricsensor 47 (see FIG. 10) provided on the conveying path disposed awayapproximately 1 pitch on the basis of the standard sheet material pitchfrom the accumulation impeller 41 detects a passage of the i-th sheetmaterial (step S103). At this time, the controller causes the encoder 43to read blade positions of the accumulation impeller 41, thusdetermining an insertion position of the i-th sheet material (stepS104). The target insertion position of this sheet material is apredetermined position within the above-mentioned insertion width. Thealready-stored sheet material pitch is read (step S105), and anarithmetic operation about the evaluation function which will be statedlater is performed (step S106). Thus, the rotating speed of theaccumulation impeller 41 is determined to obtain a proper insertionposition (step S107). The motor of the impeller is controlled to obtainthis rotating speed (step S108). Note that the sheet material pitch dataP_(i) between the sheet material finishing its insertion and the sheetmaterial just behind this sheet material are sequentially erased fromthe memory 102 in order to save the memory capacity.

Herein, in addition to the assured insertion of the relevant sheetmaterial, the insertion position of the relevant sheet material isdetermined to reduce a quantity of the pitch deviation of the next sheetmaterial to the greatest possible degree. This makes a largecontribution to the reduction in the control torque. Then, in accordancewith this embodiment, when determining the insertion position, forexample, the evaluation function J expressed by the following equationis obtained, and there is selected such a control quantity as tominimize a value of this evaluation function.

    J=(Control Quantity).sup.2 +Σ(Sheet material Pitch Scatter Quantity Produced In Consequence of Control).sup.2 (4)

Created is a formula in which the parameter in the formula (4) isexpressed by the insertion position (insertion angle) into the groove.The symbol θ_(i) is the insertion position of the i-th sheet materialwhen the accumulation impeller 41 goes on rotating at the standard speedwith respect to the insertion width ±θe determined by the formula (3)given above. If the insertion position is shifted by θc due to afluctuation in the rotating speed, it is required that the followingrelationship be established:

    -θe<θ.sub.i +θc<θe                 (5)

The control quantity θc has to fall within the following range:

    -θe-θ.sub.i <θc<θe-θ.sub.i   (6)

As stated above, each sheet material pitch P_(i) is stored in the memoryimmediately after each sheet material is taken out of the take-out unit.Accordingly, the controller for the accumulating unit is thereby capableof knowing the positions of the i-th sheet material and of thesubsequent sheet materials and calculating θ_(i) +_(1') θ_(i) +_(2'). .. at that time. Then, these items of data are employed for the control,and the evaluation function Ji for controlling the insertion of the i-thsheet material is expressed such as: ##EQU1## The second term of theformula (7) intends to weight an influence on the sheet materialssubsequent to the i-th sheet material. In such a range as to satisfy theformula (6), there is selected such θc as to minimize Ji in the formula(7). It is thus possible to perform the control assuring the insertionand taking the subsequent sheet materials into consideration. Note thatC_(k) in the formula (6) represents the weighing coefficient of thecontrol of the respective sheet materials, and n is the predicted numberof sheet materials used for the control.

Herein, there are a variety of patterns of the sheet material pitcherror, and it is difficult to output an optimal control value to anykind of patters with a fixed coefficient at all times. Obtaining thebest control result entails, as a matter of course, minimizing thecontrol torque of the stepping motor for driving the accumulationimpeller and reducing the scatter in terms of the insertion position ofthe sheet material. As a measure taken therefor, it can be consideredthat there is given a fixed coefficient adapted to perform as optimalcontrol as possible with respect to any kind of patterns of the sheetmaterial pitch error; or alternatively, the optimal control is conductedby changing the coefficient per pattern. In the former case, forexample, several hundreds to several ten thousands of sheet materialsundergo a feed test when adjusted in the factory, and, at the same time,the sheet material insertion position is observed. The coefficient ofthe above evaluation function is thereby determined to give the leastscatter in terms of the insertion position of the sheet material intothe accumulation impeller within the insertion width. In the lattercase, there are prepared a multiplicity of combinations of thecoefficients effective in the variety of patterns of the sheet materialpitch error. Pattern matching of the sheet material pitch error iseffected when movable, the coefficient of the evaluation function isselected each time, whereby more elaborate control can be attained. Inthe latter case, an application of a fuzzy rule is effective. Further,there can be also considered such a system as to change the coefficientwhile working the apparatus by adopting a method employed for learningcontrol of a neural network, AI, and the like, with the aid of ahigh-speed arithmetic unit. According to this system, a small amount ofadjustments may suffice at the initial stage, and, with the passage oftime, quite favorable results can be obtained.

FIG. 13 is a graphic chart showing effects based on the accumulationcontrol system of the sheet material inspection apparatus according tothis invention. The following are meanings of the symbols given on theaxis of the abscissa.

N.C. Control based on only the positional data of the sheet materialjust before the insertion.

F.C.1 Control based on the data about the pitch from the sheet materialon the verge of the insertion to the one located one sheet materialbehind.

F.C.2 Control based on the data about the pitch from the sheet materialon the verge of the insertion to the one located two sheet materialsbehind.

F.C.3 Control based on the data about the pitch from the sheet materialon the verge of the insertion to the sheet material located three sheetmaterials behind.

F.C.4 Control based on the data about the pitch from the sheet materialon the verge of the insertion to the one located four sheet materialsbehind.

Note that the control conditions when obtaining this result are asbelow:

    ______________________________________                                        Processing Speed:  1200 sheet materials/min                                   Number of Impeller Grooves                                                                       12 (30°)                                            Impeller Rotational Inertia                                                                      16 Kg·cm.sup.2                                    Insertion Width    7.5°                                                Sheet material Conveying                                                                         12 m/s                                                     Velocity                                                                      Sheet material Pitch Error                                                                       ±6ms, caused at random                                  ______________________________________                                    

As shown above, it can be known that the control torque of the drivingmotor decreases with an increment in the predicted number of sheetmaterials employed for the control. In this test, it can be confirmedthat a sufficient effect is obtained, wherein the predicted number ofsheet materials is 3 to 4.

As discussed above, according to the sheet material inspection apparatusin the present embodiment, when inserting the sheet material into theaccumulation impeller, it is possible to reduce the control torque ofthe motor for driving the accumulation impeller, and, therefore, ahigher-speed feed of the sheet material is attainable.

FIG. 14 is a schematic view illustrating a construction of the sheetmaterial inspection apparatus in another embodiment of this invention.Provided in this construction is an auxiliary conveying unit 6 includingan auxiliary conveying path 61 disposed just behind the take-out unit 1.This auxiliary conveying path 61 has a length sufficient to admit apassage of substantially one sheet material but is driven independentlyby an AC servo motor 62 separate from the main conveying path. Thecontroller performs an acceleration and a deceleration of the auxiliaryconveying path 61 on the basis of the pitch data of the sheet materialimmediately after the take-out unit 1. If the pitch error of the sheetmaterial immediately after the take-out unit 1 comes to a magnitudegreater than a predetermined error, the sheet material pitch iscorrected by the controller. When detecting that the sheet materialpitch P_(i) is larger (or smaller) by a given quantity than the standardpitch, the AC servo motor 62 accelerates (or decelerates) the feed froma point of time when the relevant sheet material reaches the auxiliaryconveying path 61, and a pitch error between the i-th sheet material andthe sheet material previous thereto is reduced by a predeterminedquantity. Supposing that the AC servo motor 62 has a capability toinstantaneously decelerate (accelerate) the feed of the sheet materialin the auxiliary conveying unit 6 down up to Vmin (Vmax), the pitchcorrection width Pa is given by the following formula:

    LD/V-LD/Vmax≦Pa≦LD/Vmin-LD/V                 (8)

where LD is the length of the auxiliary conveying path 61, and V is thestandard sheet material conveying velocity.

For instance, if the sheet material insertion width converted into thesheet material pitch error of the accumulation impeller is ±10% of thestandard sheet material pitch, and if the sheet material pitch errorgenerated when taken out is ±30% of the standard sheet material pitch,it follows that the accumulation impeller may absorb +10% withfluctuations in the rotating speed when having such a correctioncapability as to set Pa to ±10% of the standard sheet material pitch inthis auxiliary conveying unit 6. If the auxiliary conveying unit 6 doesnot exist, however, an error on the order of ±20% has to be absorbed bythe fluctuations in the rotating speed. In this way, the control torqueof the stepping motor when controlling the accumulation impeller can bereduced by providing the auxiliary conveying unit 6. As a result, thesheet materials can be accumulated at high speed. Further, the sheetmaterials can be accumulated at a higher speed with a combination of theabove-discussed control method of the accumulation impeller according tothe above-discussed embodiment of the present invention and the sheetmaterial pitch correction effected by this auxiliary conveying unit.

Next, the conveying system will be explained.

FIGS. 8A-8C schematically illustrate a partial construction of one unit(conveying unit) of the conveying mechanism 20. FIG. 8A is a plan view.FIG. 8B is a front view. FIG. 8C is a perspective view. The conveyingmechanism is constructed of belts 21, rollers 22 and guides 23. Twolengths of belts are provided in parallel to the conveying direction.The conveying system provides that the sheet material is held at twoportions in the crosswise direction of the feed by the belts 21 and therollers 22 and thus fed. The belts 21 are wound on drive rollers (notshown) provided in positions off the conveying surface and thus drivenat a high velocity. The rollers 22 wound with the belts 21 rotate inidling, whereby the sheet material 10 is fed between the belts 21 andthe rollers 22. A spacing between the rollers 22 is set smaller than alength of the sheet material in the conveying direction to surely feedthe sheet material 10. Some portion of the sheet material 10 is alwaysheld between the belts 21 and the rollers 22, and the driving isconducted with stability. The guides 23 are disposed at a heightsufficient to give a clearance on the order of 0.5-3 mm with respect tothe belts 21 but laid in a rail-like configuration in the crosswisedirection of (perpendicular to) the feed sheet material. The surfacematerial of the guide 23 involves the use of a resinous material and apolymer material (e.g., polytetrafluoroethylene resin) exhibiting alubricity, thereby making it possible to reduce damage to the sheetmaterial 10 due to a contact therebetween. Further, it is also possiblethat the metal-worked guide whose surface is coated with a lubricatingmaterial, or a member composed of the lubricating material is bondedthereto.

The edges of the guide 23 on both sides thereof are notched in a shapeof circular arc along the periphery of the roller shaft from the side tothe upper portion of the roller shaft. Also, the front edge of the guide23, near the upstream roller 22, has a downstream portion in theconveying direction, that is formed with an inclined surface orientedupward of the roller from the guide upper surface. The formation of thisinclined surface prevents the sheet material from entering downward ofthe guide 23. Further, the guides are provided in parallel to the beltsand assume a configuration adapted to support the sheet material with asmall width, and, therefore, even if a flexure and vibrations of thesheet material in the up-and-down directions are caused during the feed,they do not become obstacles to the feeding. This effectively preventsdamage to the sheet material 10 particularly during feeding at highvelocity.

The following are advantages of this conveying system. A force ofdeviation is not generated in the belts, and, hence, it is quite hardfor the belts to come off. Further, for this reason, the belt tension isnot required to be adjusted. The simple construction thereof requiressmall numbers of the rollers 22 and of the belts 21, and down-sizing anda reduction in terms of weight of the apparatus are attained. Noisesproduced are small even during high-speed conveying, and the sheetmaterial 10 is difficult to damage.

FIG. 15 is a view illustrating a configuration of the conveying path 20shown in FIG. 4. The conveying unit shown in FIGS. 8A-8C is constructedin such a manner that a plurality of rollers thereof are connected onthe same circular arc. When the belt is driven at a high velocity bysuch a conveying system, the belt in an arc having a radius R due to itsinertia between the rollers. When the sheet material is fed in thisstate, a centripetal force F in the radial direction acts on the sheetmaterial. Herein, F can be expressed such as:

    F=mv.sup.2 /R                                              (9)

where

m: the mass of one sheet material,

v: the conveying velocity of the sheet material (belt velocity), and

R: the curvature of the conveying path.

Also, the conveying force Fp on the sheet material is given by:

    Fp=μF+Fr                                                (10)

where

μ: the frictional coefficient between the belt and the sheet material,and

Fr: the conveying force of the roller/belt grasping portion.

In the present conveying system, it can be understood from the formulae(9) and (10) that a contact force of the sheet material on the beltincreases with a higher sheet material conveying velocity. For thisreason, it follows that one side of the sheet material between therollers is always pressed against the conveying belt, and it is possibleto avoid a rupture caused by a windage loss and a collision with theguide due to a flip of the leading edge of the sheet material.Therefore, this is advantageous especially in conveying at highvelocity. Furthermore, the following are other advantages of conveyingsystem. The force of deviation is generated in the belt, and, hence, thebelt is hard to come off. Also, for this reason, the adjustment for thebelt tension is unnecessary. Small numbers of rollers and of belts maysuffice because of the simple construction, and, consequently, thedown-sizing and the reduction in weight of the apparatus are attained.The noises produced are low even when fed at high velocity.

FIG. 16 illustrates an example of the configuration of a belt-to-beltreceiving/conveying unit in the above-mentioned conveying system in thisembodiment. In this example, the leading end of the conveying beltlocated downstream is in face-to-face relationship with the proximalportion of the belt located upstream. As a result, the guide 23 isdisposed above the belt 21 on the downstream side but under the belt 21on the upstream side.

FIGS. 17A-17C show another example of the conveying unit. FIG. 17A is aplan view. FIG. 17B is a front view. FIG. 17C is a perspective view.This conveying system is constructed so that at least one portion of thesheet material in the lengthwise direction is grasped by the belt andthe roller, and both edges thereof in the crosswise direction are guidedfrom outside the rollers. This belt is stretched between two rollers 26.Two pieces of guides 23 are provided outward in the crosswise directionof this belt. The shape of this guide is the same as that explained inFIGS. 8A-8C. In this conveying system also, the sheet material can befed at the high velocity.

FIG. 18 illustrates a combination of the conveying unit shown in FIGS.17A-17C and the conveying unit shown in FIGS. 8A-8C. This conveyingdevice takes such a construction that the rollers 26, provided upstreamand downstream, of the conveying unit shown in FIGS. 17A-17C are locatedbetween two rollers 27 with respect to the downstream-side belt 21. Withthis construction, a distance between the roller 27 and the roller 26can be decreased, and it is therefore possible to actualize theconveying system causing fewer of jams.

FIG. 19 illustrates an example where detection units 52, 53, 54 for thesheet materials are disposed along the conveying path according toembodiments of the present invention. The rollers are providedconcentratedly on one side of the conveying path, and, therefore, a sizeof the detection system can be considerably freely designed on the sidewhere the rollers do not exist. Hence, there is less constraint in termsof the size when designing the detection device. Further, the distanceto the sheet material can be freely set. The same detection device asthe conventional one can be basically disposed on the side where therollers exist. The detection device and the guide are formed into oneunited body, thereby making it possible to perform the detection inclose proximity to the sheet material surface.

FIGS. 20A-20C illustrate a construction of a conveying device 80 inaccordance with yet another embodiment of the present invention. FIG.20A is a plan view. FIG. 20B is a front view. FIG. 20C is a side view.In this embodiment, the belts are employed in place of the guides ofFIGS. 8A-8C. That is, the roller in this embodiment is composed ofordinary rollers 81 and roller members 82 each having a small diameter.A belt 83 is stretched between the rollers 81. A belt 84 is stretchedbetween the rollers 82. A clearance on the order of 0.5-3 mm is providedbetween the belts 83 and 84. With this arrangement, the belt 84 performsthe same function as that of the guide plate explained in FIGS. 8A-8C.

As described above, according to the present invention, it is feasibleto freely select a grasping mode and portions of the sheet material andalso the guide position.

As discussed above, according to the sheet material inspection apparatusof the present invention, the insertion of the sheet material into theimpeller is controlled based on the sheet material-to-sheet materialpitch. Hence, it is possible to provide a sheet material inspectionapparatus capable of performing the accumulating operation at anextremely high velocity without causing an increase in the controltorque of the motor for driving the accumulation impeller in theaccumulating unit.

Furthermore, according to the sheet material inspection apparatus of thepresent invention, the rollers and the belts cooperate to give theconveying force, and, meanwhile, the sheet material is guided by theguide plates. The sheet materials can be thereby stably fed at highvelocity using a simple construction.

It is apparent that, in this invention, a wide range of differentworking modes can be formed based on the invention without deviatingfrom the spirit and scope of the invention. This invention is notrestricted by its specific working modes except being limited by theappended claims.

What is claimed is:
 1. An apparatus for inspecting sheet materials, theapparatus comprising:conveying means for sequentially conveying aplurality of sheet materials; a rotary body, having a plurality ofgrooves formed in the periphery thereof to permit insertion of the sheetmaterials, said rotary body receiving the sheet materials one by one inrespective grooves while rotating the sheet materials conveyed from saidconveying means; accumulating means for accumulating the sheet materialsinserted into the plurality of grooves of said rotary body; detectingmeans for detecting a pitch between the sheet materials conveyed on theconveying means; and control means for controlling a rotation status ofsaid rotary body so that each of the sheet materials is inserted into apredetermined position of each of the respective grooves of said rotarybody based on the pitch between the sheet materials detected by saiddetecting means, wherein the control means controls the rotation statusof the rotary body to minimize a value obtained by adding a controlquantity related to an insertion position of one of the sheet materialsto a result of weighing an influence of the one of the sheet materialsonto a subsequent sheet material.
 2. The apparatus of claim 1, whereinsaid control means for controlling said rotation status of said rotarybody controls a rotating speed of said rotary body based on the pitchdetected by said detecting means.
 3. The apparatus of claim 1, whereinsaid conveying means includes an auxiliary conveying means for conveyingthe sheet materials, driven independently of said conveying means, andsaid control means includes means for changing a conveying velocity ofthe sheet materials on said auxiliary conveying means based on the pitchdetected by said detecting means.
 4. The apparatus of claim 2, whereinsaid control means includes:storage means for storing information of thepitch between sheet materials; arithmetic means for effecting apredetermined arithmetic operation; and mechanism control means forcontrolling insertion of one of the sheet materials into said rotarybody based on an arithmetic result given by said arithmetic means.
 5. Asheet material conveying device for conveying sheet materials, the sheetmaterial conveying device having a plurality of conveyors, each of saidconveyors comprising:a pair of rollers disposed a predetermined distanceaway from each other; a driving belt stretched between said pair ofrollers and wound on said rollers through a predetermined angle; a guidemember disposed between said pair of rollers so that an upper surface ofsaid guide member is located a predetermined constant spacing from aconveying surface of the driving belt; and drive means for driving saiddriving belt, wherein the conveying surface of the driving belt touchesthe rollers while the driving belt travels between the rollers, andwherein the sheet materials touch the conveying surface of said drivingbelt and the upper surface of said guide member while being conveyed bythe driving belt.
 6. The device of claim 5, wherein an upstream one ofsaid plurality of conveyors has two first rollers on first roller shaftsprovided upstream and downstream, respectively, and two first guidemembers disposed inward of said first rollers in a directionsubstantially orthogonal to a conveying direction, and wherein anadjacent downstream conveyor has two second rollers on second rollershafts, one provided upstream and another provided downstream, and twosecond guide members disposed outward of said second rollers in thedirection substantially orthogonal to the conveying direction.
 7. Thedevice of claim 6, wherein said upstream second roller shaft of saidadjacent downstream conveyor serves as said downstream first rollershaft of said upstream one of said plurality of conveyors.
 8. The deviceof claim 6, wherein each of said first and second guide members has acurved portion extending from a side portion to an upper portion of eachof said first and second roller shafts and is formed with an inclinedsurface at an upstream front edge.
 9. The device of claim 5, whereinsaid plurality of conveyors are disposed so that a plurality ofconveying surfaces defined by a plurality of driving belts form asubstantially arc surface having a substantially common center ofcurvature.
 10. An apparatus for inspecting sheet materials, theapparatus comprising:a conveyor for sequentially conveying a pluralityof sheet materials; a rotary body, having a plurality of grooves formedin the periphery thereof to permit insertions of the sheet materials,the rotary body receiving the sheet materials one by one in respectivegrooves while rotating the sheet materials conveyed from the conveyor;an accumulator for accumulating the sheet materials inserted into theplurality of grooves of the rotary body; a detector for detecting apitch between the sheet materials conveyed on the conveyer; and acontroller for controlling a rotation status of the rotary body so thateach of the sheet materials is inserted into a predetermined position ofeach of the respective grooves of the rotary body based on the pitchbetween the sheet materials detected by the detector, wherein thecontroller minimizes a value obtained by adding a control quantityrelated to an insertion position of one of the sheet materials to aresult of weighing an influence of the one of the sheet materials onto asubsequent sheet material.
 11. The apparatus of claim 10, wherein saidcontroller controls a rotating speed of said rotary body based on thepitch detected by said detector.
 12. The apparatus of claim 11, whereinsaid controller includes:a storage for storing information of the pitchbetween sheet materials; an arithmetic operator for effecting apredetermined arithmetic operation; and a mechanism controller forcontrolling insertion of one of the sheet materials into said rotarybody based on an arithmetic result given by said arithmetic operator.13. The apparatus of claim 10, wherein said conveyor includes anauxiliary conveyor for conveying the sheet materials, drivenindependently of said conveyor, and said controller includes a conveyingvelocity changer for changing the conveying velocity of the sheetmaterials on said auxiliary conveyor based on the pitch detected by saiddetector.
 14. A sheet material conveying device for conveying sheetmaterials, the sheet material conveying device having a plurality ofconveyers, each of said conveyors comprising:a pair of rollers disposeda predetermined distance away from each other; a driving belt stretchedbetween said pair of rollers and wound around said rollers through apredetermined angle; a guide member disposed between said pair ofrollers so that an upper surface of said guide member is located apredetermined constant spacing from a conveying surface of the drivingbelt; and a driver for driving said driving belt, wherein the conveyingsurface of the driving belt touches the rollers while the driving belttravels between the rollers, and wherein the sheet materials touch theconveying surface of said driving belt and the upper surface of saidguide member while being conveyed by the driving belt.
 15. The device ofclaim 14, wherein said plurality of conveyors are disposed so that aplurality of conveying surfaces defined by a plurality of driving beltsform a substantially arc surface having a substantially common center ofcurvature.
 16. The device of claim 14, wherein an upstream one of saidplurality of conveyors has two first rollers on first roller shafts andtwo first guide members disposed inward of said first rollers in adirection substantially orthogonal to a conveying direction, and whereinan adjacent downstream conveyor has two second rollers on second rollershafts and two second guide members disposed outward of said secondrollers in the direction substantially orthogonal to the conveyingdirection.
 17. The device of claim 16, wherein said upstream secondroller shaft of said adjacent downstream conveyor serves as saiddownstream first roller shaft of said upstream one of said plurality ofconveyors.
 18. The device of claim 16, wherein each of said first andsecond guide members has a curved portion extending from a side portionto an upper portion of each of said first and second roller shafts andis formed with an inclined surface at an upstream front edge.